Field of the Invention
The present invention relates to an organic light emitting device, and more specifically, to an organic light emitting device including a hole connection layer between light emitting layers and method for manufacturing the same.
Discussion of the Related Art
An organic light emitting device (hereinafter, referred to as OLED) is an electronic device that emits light in response to an applied potential. The structure of the OLED typically includes an anode, an organic EL medium, and a cathode, in sequence. Generally, the organic EL medium provided between the anode and the cathode includes an organic hole transport layer (HTL) and an electron transport layer (ETL). Holes and electrons are recombined to emit light in the ETL near the interface of HTL/ETL. Tang, et al. demonstrated a very effective OLED using such a layer structure in “Organic Electroluminescent Diodes,” Applied Physics Letters, 51, 913 (1987) and in commonly assigned U.S. Pat. No. 4,769,292.
In addition, as disclosed in Adachi et al., “Electroluminescence in Organic Films with Three-Layer Structure,” Japanese Journal of Applied Physics, 27, L269 (1988) and Tang et al., “Electroluminescence of Doped Organic Thin Films,” Journal of Applied Physics, 65, 3610 (1989), there is a three-layer type OLED including an organic light emitting layer (hereinafter, referred to as LEL) between HTL and ETL. Generally, LEL contains a host material doped with a guest material. In addition, there are other multilayer-type OLEDs including additional functional layers, such as a hole injection layer (hereinafter, referred to as HIL), and/or an electron injection layer (herein, referred as EIL), and/or an electron blocking layer (EBL), and/or a hole blocking layer (HBL). At the same time, various types of EL materials are synthesized, and then used for an OLED. These novel structures and novel materials further improve the device performance.
Meanwhile, a soluble hybrid OLED device for a soluble type process is disclosed in Tomoyuki Higo, et al. “A High-Performance Hybrid OLED Device Assisted by Evaporated Common Organic Layers,” IDW '311 (2010). Referring to FIG. 1, for large-area processing, HIL, HTL and LEL(R, G) are patterned on an anode through a soluble process, and a hole connection layer, a blue common layer (Blue (B)), ETL, EIL and a cathode are formed through vacuum thermal evaporation (VTE), without masks.
The charge balance of respective R, G, and B elements needs to be optimized for optimizing the lifetime and improving the color coordinates of the OLED device, but the optimization of the charge balance is not easy to implement in the above-described structure in which HTL, the hole connection layer, the blue common layer, ETL, and EIL are commonly used.
When the charge balance is not optimized, charges may accumulate in any one interface to induce the exciton quenching, causing a problem in the stability of the OLED device. Currently, in the red and green soluble hybrid OLED device having a bipolar hole connection layer, holes may accumulate in the interface between a light emitting layer and a hole connection layer to induce a charge accumulation phenomenon, causing a bad influence on the lifetime of the OLED device, and the deep blue wavelengths limited in the hole connection layer may degrade the color characteristics of the OLED device.